Huntington's disease (HD) and Parkinson's disease (PD) are neurodegenerative diseases. The neuropathological, neurochemical and behavioral hallmarks of HD can be replicated in the non-human primate by stereotaxic excitotoxic lesions of the caudate-putamen (Isacson et al. 1989). In a MPTP chronic lesion model of PD, we are currently pharmacologically testing drugs for therapeutic effects in combination with transplantation of fetal neurons. Behavioral testing of the HD and PD models is therefore of utmost importance for developing a neurobiological basis for new treatments of neurodegenerative disease. The HD model determines the neurological basis for basal ganglia dependent dyskinesia. This year we will continue our lesion and transplantations studies in combination with PET and MRI studies to develop a therapy against the symptoms seen in HD and PD.